A variety of products may be made from webs of sheet materials. Webs are very long lengths of sheet material that are generally supplied in roll form. Paper, plastic sheets, fabric, and sheet metal are examples of materials that may be provided in web form. Processing material in web form may lend itself to high speed production of large numbers of items.
Web processes may take advantage of the ability to rapidly feed the web material to successive processing stations in a substantially continuous fashion. The processing stations may perform any of a variety of operations on the web, such as punching, cutting, sealing, or imprinting. Generally each processing station will perform a single type of operation. A series of processing stations may be arranged such that the raw web material is supplied to the first of the series of stations. The processed result of each of the series of stations may be supplied to the next station until a finished article emerges from the last of the series of stations.
Bags and pouches are examples of items that can be made using a web process. One process for making pouches uses two webs of raw sheet material. The two materials may be identical or dissimilar. One processing step, possibly the first step, is to laminate the two sheets along a seam line to create a pouch. The final processing step may be a cutting operation to separate the web of pouches into individual items.
It will be appreciated that each processing station must process the web at the same average rate. Accumulators may be used to absorb momentary differences in the speed at which the web is advancing through a processing station. But ultimately the time available for each processing station to process the same number of items is the same.
Returning to the example of the laminated pouch, the process for laminating the two webs may require that a seaming iron press the two webs together for a period of time, such as one second. This may require stopping the web in the processing station for a period of time that it takes to laminate the seam. As a result, the laminating station might produce one item per second. To increase the production rate of a laminating station, the seaming iron may be arranged so that more than one item is formed along the length of the web in a single laminating operation. For example, if the seaming iron produces twenty pouches along the length of the web, the laminating station might produce twenty items per second.
It will be appreciated that more than one item may be produced across the width of the web. For example, the seaming iron might produce four pouches across the width of the web increasing the production rate to 80 items per second. Since this merely requires duplication of the processing mechanism across the width, only the processing of one item across the width will be discussed for clarity. However, it is to be understood that all the web operations that are discussed may be extended to any number of items across the width of the web.
A web process that includes a processing station that requires stopping the web for a significant length of time and which produces multiple items along the length of the web to increase the production rate may create a dilemma for other processing stations in the web process. It may be desirable to minimize the starting and stopping of the web. Thus it may be desirable for each processing station that has to stop the web to stop the web at the same time and for the same duration.
Again returning to the example of the laminated pouch, the pouch may include one or more features that require punching operations, such as a hanging hole, a tear notch, or rounded corners. If the web moves against the punch while the punch is penetrating the web, the web may tear or crumple. Therefore, a punching operation that punches the same number of items along the length of the web as are produced by the laminating operation might be desirable. However, the tooling for punching may be more difficult or costly to replicate along the length of the web than the seaming iron tooling.
It would be desirable to have a punching station for a web and that does not require the use of multiple punch tooling along the length of the web.